D-Sub Connector Pinout Reference: DB9, DB15, DB25, DB37, DB50

D-Sub connector selection and pinout assignment across DB9, DB15, DB25, DB37, and DB50 variants comes down to three engineering decisions:

Key Takeaways

• Cinch/ITT shell-letter naming (DE-9, DA-15, DB-25, DC-37, DD-50) is the technically correct designation — "DB9" and "DB15" are shortcuts that cause ordering errors with custom suppliers.
• DB9 (DE-9) dominates RS-232 and CAN bus applications per TIA/EIA-232-F and CiA 303-1 — the pinouts differ entirely, so the same connector serves both standards with no compatibility.
• DB15 has two distinct variants — DA-15 standard density (legacy game port, MAU/AUI Ethernet) and HD-15 high density 3-row (VGA per VESA), which share no pinout despite the same shell.
• Standard-density D-Sub contacts carry up to 5 A at commercial spec (7.5 A peak); high-density contacts (HD-15, HD-26) drop to 1–2 A due to smaller contact geometry.
• MIL-DTL-24308 specifies military D-Sub with machined contacts, while IEC 60807-3 covers commercial — for aerospace, mil-spec, or harsh-environment applications, MIL-DTL-24308 acceptance is required.

Engineering rule of thumb: Order D-Sub by Cinch shell letter and pin count (e.g., "DE-9, male pins, female shell, machined contacts") not the "DB9" shortcut — the shortcut leaves ambiguity around DA-15 vs HD-15 and contact type.

D-Sub Naming Convention: Why "DB9" Is Technically Wrong

The D-subminiature family uses shell-letter naming from the original Cinch/ITT specification — letter (E, A, B, C, D) identifies the shell size, number identifies contact count: DE-9, DA-15, DB-25, DC-37, DD-50.

The "DB" prefix migrated into general usage because original IBM PC documentation labeled the 25-pin serial port "DB-25," and the convention spread to all shell sizes. This is technically incorrect for every shell except B.

Naming matters in custom procurement because "DB15" is ambiguous: it can refer to DA-15 (two rows, legacy game port and MAU Ethernet) or HD-15 (three rows, VGA). Specifying by Cinch designation removes the ambiguity at quote stage.

DB9 (DE-9) Pinouts: RS-232, CAN bus, and Industrial Variants

DE-9 is the most-deployed D-Sub variant, serving two dominant signaling standards with entirely different pinouts.

RS-232 (TIA/EIA-232-F) places TXD, RXD, signal ground, and modem-control signals (DTR, DSR, RTS, CTS, DCD, RI) on the fixed assignment shown in the pinout table below. The DCE side mirrors the data lines (TXD becomes input, RXD output) — the root of most RS-232 cable troubleshooting confusion.

CAN bus (CiA 303-1) places CAN_H on pin 7, CAN_L on pin 2, CAN_GND on pin 3, and optional CAN_V+ on pin 9. Pin 2 is RXD in RS-232 but CAN_L in CAN — the connectors are physically identical but the cables are not interchangeable.

For industrial DE-9 outside RS-232 and CAN, pinout is application-specific — always validate continuity per the equipment pinout, not the RS-232 default.

DB15 Pinouts: DA-15 Game Port vs HD-15 VGA

DB15 refers to two different connectors that share the name but nothing else.

DA-15 (standard density) uses 15 contacts in two rows (8 + 7) — historically the IBM PC game port, MAU/AUI 10BASE5 Ethernet, and Apple Macintosh video. Modern usage is rare outside legacy industrial equipment.

HD-15 (high density) uses 15 contacts in three rows (5 + 5 + 5) within the same DE shell — the VGA connector per VESA DDC. Pins 1–3 carry R/G/B analog video (75 Ω), pins 6–8 are color returns, pin 12 (SDA) and pin 15 (SCL) carry the I²C DDC channel for monitor identification, pin 13 is HSync, pin 14 is VSync.

Custom procurement should always specify DA-15 or HD-15 explicitly. Connector keying is incompatible — an HD-15 plug will not seat in a DA-15 receptacle.

DB25 Pinouts: RS-232 Full, IEEE 1284 Parallel, and SCSI-1

DB-25 (B shell, 25 contacts) was the original RS-232 connector before DE-9 became dominant, and remained the standard for parallel printer ports through the 2000s.

RS-232 per TIA/EIA-232-F uses TXD on pin 2, RXD on pin 3, signal ground on pin 7, DCD on pin 8, DTR on pin 20, RI on pin 22, and RTS/CTS/DSR on pins 4–6. Pin 1 is Protective Ground (PG), bonded to chassis via the cable shield.

IEEE 1284 parallel (host side) uses pin 1 as nStrobe, pins 2–9 as Data 0–7, pin 10 as nAck, pin 11 as Busy, and pins 18–25 as ground returns. The standard defines four operating modes (Compatibility, Nibble, Byte, ECP/EPP) over the same pinout.

SCSI-1 used DB-25 in some legacy implementations (Macintosh SCSI), though the common SCSI-1 connector is the 50-pin Centronics.

DB37 and DB50: Industrial Multi-Channel and Legacy SCSI

DC-37 (DB37) and DD-50 (DB50) are larger D-Sub shells used in industrial automation, multi-channel instrumentation, and legacy SCSI. Pinouts are application-specific without dominant industry standards.

DC-37 appears in industrial PLC I/O modules, multi-axis motion control (4–6 servo channels per connector), test-equipment trigger ports, and legacy parallel ATA. Pin assignment is dictated by the equipment manufacturer's interface spec.

DD-50 is most commonly associated with internal SCSI-1 wide differential interfaces and high-channel-count industrial automation. The 50 contacts across three rows are space-efficient for multi-signal cabling, but pin density requires careful wire dressing at termination.

For custom assemblies in these shells, the cable spec must include the equipment manufacturer's pinout map plus shield termination and any differential pair groupings. Both shells support standard 5 A contacts; combo D-Sub variants with size 8 or 12 power contacts carry 25–40 A for mixed-signal applications.

Termination, Backshells, and Shielding for D-Sub Cable Assemblies

D-Sub termination has three options with different field-failure modes.

Solder cup is the legacy default — wire soldered into a cup at the back of each contact, acceptable for prototypes and low-volume builds. Vulnerable to solder-joint fatigue under vibration, bounded by IPC/WHMA-A-620 hand-soldering acceptance. The crimping vs soldering comparison covers the reliability tradeoff.

Machined-pin crimp uses removable machined contacts crimped to the wire and inserted with extraction tools. Industry standard for production volumes, mil-spec applications (per AS39029), and any application requiring field pin replacement. Required for MIL-DTL-24308.

Insulation Displacement Connection (IDC) mass-terminates ribbon cable to the connector in a single press. Used only in high-volume legacy applications.

Backshells provide strain relief and shield termination. Metal hood backshells (zinc die-cast) bond the cable braid to the connector shell and to chassis ground — required when EMI matters. Plastic backshells suffice for unshielded low-frequency applications only.

For custom cable assemblies carrying RS-232 above 9600 baud, RS-422/485, or any data above 1 Mbps, specify a metal backshell with 360° shield termination.

D-Sub Variants Overview

DB9 RS-232 Pinout (DTE Side)

Specification FAQ

What's the difference between DB9 and DE-9?

DB9 and DE-9 are the same physical connector — 9 contacts in the E-size D-Sub shell. DE-9 is the Cinch/ITT designation; DB9 is the IBM PC shortcut. The terms are interchangeable, but custom procurement should use DE-9 to eliminate ambiguity around stamped-vs-machined contacts or shell finish variants.

What's the difference between DB15 and HD-15?

"DB15" is ambiguous. It can refer to DA-15 (15 contacts in two rows within the A-size shell, for legacy game ports and MAU Ethernet) or HD-15 (15 contacts in three rows within the smaller E shell, for VGA per VESA DDC). The two are not physically interchangeable — keying and shell size differ. Always specify DA-15 or HD-15 explicitly.

Solder cup vs. crimp vs. IDC — which D-Sub termination should I specify?

For production volumes over 100 units or applications subject to vibration, specify machined-pin crimp — the industry standard for reliable D-Sub termination and required for MIL-DTL-24308. Solder cup is acceptable for prototypes and low-volume builds. IDC is used only with ribbon cable. The common connector types guide covers termination selection across the broader connector landscape.

Are D-Sub connectors still used in new designs?

Yes, in specific verticals. Industrial automation (PLC I/O, drives), test equipment (oscilloscope sync, sensor cabling), aerospace (MIL-DTL-24308), legacy serial communications, and machine vision sync/trigger still specify D-Sub. RS-232 over DE-9 remains common in industrial field equipment where USB serial-bridge adapters introduce latency. For consumer applications, D-Sub is effectively obsolete.

What MOQ and lead time apply to custom D-Sub cable assemblies?

Prototype quantities (under 50 units) for custom D-Sub assemblies typically deliver in 2–3 weeks with first-article continuity, hi-pot, and per-pin assignment verification. Production runs (500+) move to dedicated tooling and run 4–6 weeks. Provide connector designation (Cinch shell letter plus pin count), gender, contact type, backshell, full pinout map, and wire AWG for a quote.

D-Sub connectors remain a durable, well-specified family — standards (TIA/EIA-232-F, IEEE 1284, VESA DDC, MIL-DTL-24308) are stable and pinouts well-documented. Custom D-Sub cable assemblies succeed or fail on three points: ordering by Cinch shell designation to eliminate ambiguity, specifying termination method appropriate to production volume and reliability, and using metal backshells with 360° shield termination wherever EMI matters. Validate every custom wire harness assembly against the equipment manufacturer's pinout, not generalized references.